These studies are designed to evaluate the clinical benefits achieved by iron chelation in patients with chronic iron overload. Desferrioxamine is administered by subcutaneous infusion and iron removed is determined by quantitation of urinary iron excretion and careful recording of the total iron administered by transfusion. Those patients who have no evidence of cardiac disease are randomized to receive either ascorbic acid (3 mg/kg) or placebo. Sixty-one patients are now included in our long-term chelation trial and, of these, forty-nine have been randomized to the ascorbic acid trial. Cardiac function is assessed by 24-hour recordings of the cardiac rhythm, echocardiography, and radionuclide cineangiography. Radionuclide cineangiography provides a very sensitive index of cardiac function in that the majority of patients who have received over 100 units of blood failed to increase their ejection fraction during exercise in the normal fashion. Follow-up radionuclide cineangiograms have been obtained in 19 patients restudied at intervals averaging 17 months. Most patients who had received more than 200 units of blood prior to the first study exhibited cardiac deterioration over the interval between the two studies while those who had received fewer than 200 units exhibited stable cardiac function.